Summer 2007 Workshop
in Biology and Multimedia
for High School Teachers
Why Can’t We Grow New
Arms?
An Introduction to Stem Cells and
Regeneration
Image by mila zinkova from commons.wikimedia.org
http://en.wikipedia.org/wiki/Image:Sea_star_regenerating_legs.jpg, image by Mila Zankova
Greek myth says that zeus
had prometheus chained to
a rock for bringing fire to
humans. Every day an
eagle would come and eat
his liver. By the time the
eagle came back the next
day, the liver had grown
back.
Your liver can
regenerate too!
Will There be a day
When your arm or leg
will grow back?
http://commons.wikimedia.org/wiki/Image:Koeln_wrm_1044.jpg
You have probably heard that sea stars
can grow a new arm if they lose one, or
even that a lost arm can grow into a
whole new sea star.
Did you know that salamanders can also
regenerate lost limbs?
This probably makes you wonder:
“Why can’t we grow new
arms?”
In order to answer that
question, You will need to
understand a little bit about
how the salamander is able to
regrow an arm and how your
arm is formed in the first
place.
Lesson Outline
I.
II.
III.
IV.
V.
What are stem cells and where do they come
from?
How does a salamander regenerate a lost
arm?
Why can’t we grow a new arm?
What do stem cells have to do with limb
development and regeneration?
Can stem cells be used to grow new limbs?
These are the questions you should be able to answer by the end of
this lesson.
As you proceed through the lesson, click on the green links to answer the questions on
your worksheet. As you scroll over the links, some of them have instructions as to
where on the page you should look for the answers.
I. What are stem cells and
where do they come from?
A. You have
undoubtedly heard
of stem cells. They
are in the news all
the time, but what
exactly is a stem
cell?
http://commons.wikimedia.org/wiki/Image:Mouse_embryonic_stem_cells.jpg
Mouse embryonic stem cells
Learn about stem cells
Answer question 1
I. What are stem cells and
where do they come from?
B. There are two types
of stem cells,
embryonic and
adult. Find out
how both are
isolated, some
similarities, and
some differences.
http://commons.wikimedia.org/wiki/Image:Stem_cells_diagram.png
Pluripotent, embryonic stem cells originate as inner mass cells with in a blastocyst. The stem
cells can become any tissue in the body, excluding a placenta. Only the morula's cells are
totipotent, able to become all tissues and a placenta.
Embryonic vs. Adult Stem Cells
Where the cells are found
Answer question 2
II. How Does a salamander
Regenerate a Lost Arm?
A. Imagine if humans
could grow new
limbs after
amputation. Some
salamanders can
do just that.
Photograph taken by Patrick Coin
http://commons.wikimedia.org/wiki/Image:Plethodon_cylindraceusPCCA20060409-3183A.jpg
Read about limb regeneration in salamanders
Visual of limb regeneration in salamander
Limb Regeneration Movie
Answer questions 3-6
II. How Does a salamander
Regenerate a Lost Arm?
B. Review the basic steps of limb regeneration
1. An epidermal layer covers the wound.
2. Cells in the stump become unspecialized and
accumulate under the epidermis. This
structuure is the blastema.
3. The blastema elongates and flattens while cells
are differentiating.
4. Finally new bones form and the limb pattern is
back to normal.
5. The new limb grows and looks just like a normal
limb.
III. Why Can’t We Grow a New
Arm?
A. First take a look at how a vertebrate
limb develops in the first place.
Vertebrate Limb Development
Answer questions 7-9
III. Why Can’t We Grow a New
Arm?
As you can see, creating an
arm is a very complex
process that requires a
number of different genes.
Each step can trigger the
next, and more and more
genes and environmental
factors get involved.
http://commons.wikimedia.org/wiki/Image:Limb_bud.pngorg by Peter Znamenski
III. Why Can’t We Grow a New
Arm?
B. It is still unclear why salamanders can
regenerate limbs while mammals and
other vertebrates cannot.
C. It may have something to do with the
complexity, but there is more to it than
that.
Why do we form a scar instead of a new limb?
Answer question 10
IV. What do stem cells have to
do with limb development and
regeneration?
Now that you know what stem cells are, how a
limb develops and how a salamander’s limb
can regenerate, you may be wondering…
What do stem cells have to do with limb
development and regeneration?
IV. What do stem cells have to do
with limb development and
regeneration?
A. Remember that stem cells are cells that
can self-renew and make cells that can
differentiate.
This image shows
how a
hematopoietic stem
cell (an adult blood
stem cell) can
differentiate into all
of the different types
of blood cells.
http://stemcells.nih.gov/info/basics/basiImage courtesy of HINcs4.asp
IV. What do stem cells have to do
with limb development and
regeneration?
B. In order for limbs (or any other body part) to
develop, the stem cells must receive the
proper signals. Each organ requires
different signals or a different order of
signals. So, during development, stem cells
for blood will receive different information
than those for skin or neurons.
To get a better Idea of this concept play the
virtual stem cell laboratory from children’s
Hospital boston
Answer questions 11-12
IV. What do stem cells have to do
with limb development and
regeneration?
C. In salamander limb regeneration, it is
unclear whether stem cells are
involved, but it is known that there are
some in the tissue that may contribute.
D. We know that when a human muscle
is damaged stem cells are responsible
for repair.
IV. What do stem cells have to do
with limb development and
regeneration?
E. Put together all of the information you
now have about stem cells,
development, and regeneration to
figure out what scientists might want to
research in order to promote limb
growth in humans.
Answer question 13.
This leads us to our final
question…
V. Can Stem Cells Be Used to
Grow a New Arm?
Image by emo_boy from http://www.abstractinfluence.com/forums/album_pic.php?pic_id=8414
A.
Many scientists are
working on this
problem right now.
They are studying
frogs, salamanders,
sea stars, and even
mice to figure out how
they can regenerate
limbs or other body
parts.
Photo Credit:US National Oceanic and Atmospheric Administration
http://upload.wikimedia.org/wikipedia/commons/b/b1/Reef0296.jpg
Image from http://commons.wikimedia.org/wiki/Image
:Mus_Musculus-huismuis.jpg#filecommons.wikimedia.org
http://commons.wikimedia.org/wiki/Image:Spiral_Salamander.jpg#file
Now find an article about
studies into limb regeneration.
Read the Article and write down
the source. Then, summarize the
article and hand it in with your
“Stem Cells and Regeneration”
worksheet.
end
Extension,
Learn More,
References
extension
Use some of the links below to answer question I. Then, write about your own opinions. Be sure to explain how you feel
and give reasons for your opinion.
I.
II.
Why are some
people opposed
to stem cell
research?
How do I feel
about stem cell
research and
use?
htt p://www .l on gevi ty meme .or g/t o pics/ st e m_cel l s _a n d _r ege n e r a t iv e_me
d ici n e .cf m
Op/Ed p iece on St e m Cell re s ear ch
htt p://s t e mc ell .s t a n fo r d .e du/ 10 1/
Rev iew of e th ical de ba t e
htt p://www .h cs .h arva r d .e du/ st e mcel l /
Ha r va r d Col l ege St e m C ell S oc ie t y
htt p://s t e mc ells .n ih .gov/ in f o/e th ics .asp
NIH St e m C ell We b s it e re view o f et h ics i n s t e m cell
r esea r c h
htt p://www .s t e mc ells .ca/
l is t of d iffe r e nt et h ical o pin io n s a n d es s ays
htt p://www .s t e mc ellr esea r c h .or g/
e th ic al op in io n s , viewp oint aga in st des tr u ct io n of h u ma n e mb ry o
Learn More
If you would like more information on stem cells, regeneration or development, go back to any of
the links in this presentation or check out some of the following:
•
The book Mutants by Armand Marie Leroi discusses human development through mutation. It is full
of interesting stories and science.
•
•
http://www.unews.utah.edu/p/?r=050306-6 - article about research grant at University of Utah
http://www.regen.iupui.edu/research_appendage.asp - information about research on limb
regeneration at Indiana University
http://discoverysedge.mayo.edu/regenerative_biology/index.cfm - online research magazine from the
mayo clinic
http://www.mirm.pitt.edu/ - McGowan Institute for Regenerative Medicine From University of
Pittsburgh
•
•
•
•
•
http://www.isscr.org/public/selected_topics.htm - International Society for Stem Cells
http://stemcell.stanford.edu/101/ - Stanford Institute for Stem Cell biology and Regenerative Medicine
http://www.hsci.harvard.edu/ - Harvard Stem Cell Institute
References
•
•
•
•
•
•
•
Amphibian Limb Regeneration http://www.uoguelph.ca/zoology/devobio/210labs/regen1.html
Commons.wikimedia.org
Morrison, Jamie L. et al “Salamander limb regeneration involves the activation of a multipotent skeletal
muscle satellite cell population” JCB 30 January 2006 http://www.jcb.org/cgi/content/full/172/3/433
Salamanders Re-grow Lost Limbs, Could Human Medicine Benefit From Understanding Regeneration?
Science Daily 1 April 2007 http://www.sciencedaily.com/releases/2007/03/070330111307.htm
Stem Cell Basics: What are adult stem cells? . In Stem Cell Information [World Wide Web site]. Bethesda,
MD: National Institutes of Health, U.S. Department of Health and Human Services, 2006 [cited Wednesday,
July 18, 2007] Available at http://stemcells.nih.gov/info/basics/basics4
Stocum, David L. Biology and Medicine: An Overview 1 July 2004
http://www.cellscience.com/Reviews1/Regenerative_Biology_and_Medicine.html
Vertebrate Limb Development--an Example of the Development of Body Parts
http://www.indiana.edu/~oso/evolution/limbs.htm